F35 High

Euroterm F35 Fault Code

The Euroterm F35 fault code means: your boiler has detected an issue with the electricity supply entering your home, meaning the power quality is not stable enough for the boiler to operate safely.. It appears on 1 Euroterm model in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Faulty mains frequency
Typical repair cost £100-£350 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Euroterm models that show the F35 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Euroterm F35 fault code information on this page is sourced and cross-checked against the official Euroterm service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026